Touch screens comprise user-interactive electronic displays. Touch screens provide graphical user interface (GUI) operability by direct user interactions with portions of the information being displayed. The user interactions allow direct user control over selecting information to be displayed on the touch screen and the appearance of the displayed information, including electronic drawing applications. As touch screens obviate components otherwise needed for GUI functionality, they are particularly useful in small form factor, lightweight, often battery-powered electronic devices such as smart phones and tablet computers, etc. Various types of touch screens are in current use.
Capacitive touch screens have superior accuracy and responsiveness characteristics relative to other common types. Capacitive touch screen displays have an electrically insulating transparent display surface such as glass or plastic covered by an array of transparent (or microscopic) conductors, which develop an electrostatic field over the display surface. Users may interact with capacitive touch screens using their finger digits or a pen type or stylus device. Styli, pens and fingers have their own capacitance or active characteristics, which effectively enable and affect their use for signaling with the touch screen display. When a user touches (or in some cases, nearly touches or gestures in proximity with) the display surface with the stylus or finger, the electrostatic field is distorted detectably by the capacitance caused by the interaction.
The distortion in the electrostatic field may be detected as a measured change in a capacitance value at the horizontal (x-axis) and vertical (y-axis) position of contact of the stylus or finger with respect to the planar rectangular display surface. The position of contact may correspond to the position of at least a pixel in an interactive image rendered on the display.
For example, a box shaped image feature labeled “enter,” “go,” “yes” or “no,” “get,” “cancel,” “stop,” etc. shown in the rendered screen image may comprise a GUI “button” with which a corresponding user input is actuated by touching the box with the stylus or finger. The user input corresponding to a programmed selection is sent to a controller module based on the touch at the detected location. The controller may be operable for calling, triggering, initiating, controlling, computing, performing, executing or halting a processing function corresponding to the programmed selection.
The terms “pen” and “stylus” (and their respective plurals “pens” and “styli”) may be used herein synonymously, interchangeably and/or equivalently. Capacitive and active pens are in current use, each of which typically operates over an upper surface of a capacitive touch screen. Capacitive pens (also called “passive” pens) are typically operable in contact with the touch screen surface.
Capacitive pens are implemented conventionally by scanning lines and thereby detecting an area or region of a part of the screen over which the pen top contacts the surface, the (x, y) coordinates of a centroid of the detected contact area and a size “z” of a circle with which a tip of the pen makes contact with the screen surface. Conventional capacitive pens are operable for reporting simply the detected area, (x, y) centroid coordinates and z size to an operating system (OS) of the touch screen device and applications running therewith. While conventional capacitive pens are operable for effectively substituting for a user's finger to signal the touch screen panel, they lack capability for reporting additional information or communicating a change from one mode of operation, such as “writing,” to another mode of operation, such as “erasing.”
Current active pens on the other hand may be operably implemented to report additional information, unavailable from conventional capacitive pens, which may be useful to the touch screen device OS and/or applications. For example, active pens are operable for communicating a change from one mode of operation to another, such as from “writing” to “erasing.” Additional useful information active pens may report include data relating to the shape of a tip of the pen, an angle of the pen tip relative to the touch screen surface, one or more “buttons” or other operable feature actuators of the active pen. The actuators enable or trigger special or specific features available from the active pen. The special features available from active pens may include an operable eraser feature, writing color selection, type selection, model or characteristic selectivity, pressure data, tip weight or thickness selectivity and/or data relating to an angle of the longitudinal axis of the pen as it is held or maneuvered by the user relative to the planar surface of the touch screen.
While such additional information and mode changes current active pens can report may be useful, the active pens are significantly more expensive than capacitive pens. Moreover, active pens require associated active circuits and communicative interconnectivity such as a dedicated wireless radio or infrared channel for data exchange with the pad device, which adds undesirable complexity as well as higher cost.
Approaches described in this section may, but have not necessarily been conceived or pursued previously. Unless otherwise indicated, approaches mentioned (or issues identified in relation thereto) should not to be assumed as admitted or as recognized in any alleged prior art merely by inclusion in this section.